LLMChess

Generates legal chess moves by prompting OpenAI language models (gpt-3.5-turbo or gpt-4) with the current board state, then parsing the LLM's text output into valid moves. The system maintains game state on the client side and sends the full board position to the LLM with each turn, relying on the model's chess knowledge to produce legal moves without explicit move validation against a rules engine.

Generates natural-language explanations of AI moves by extracting reasoning from the LLM's output during move generation. The system logs these explanations in a right-side pane, allowing players to understand the strategic intent behind each move without requiring a separate analysis pass. This leverages the LLM's ability to articulate reasoning as part of its move selection process.

Adjusts AI move strength by selecting between gpt-3.5-turbo (weaker, faster, cheaper) and gpt-4 (stronger, slower, more expensive) based on player performance or explicit selection. The system may also implement prompt-level difficulty adjustments (e.g., instructing the LLM to play 'cautiously' or 'aggressively'), though the exact mechanism is not documented. This allows the same system to serve beginners through intermediate players without requiring multiple chess engines.

Maintains the current chess board state in the browser (likely using JavaScript and HTML5 Canvas or SVG), renders the board visually, handles user input for move selection (click-to-move or drag-and-drop), and updates the display after each move. The system persists game state in memory during a session and provides UI controls for starting new games and ending the current game. No backend persistence is documented, so games are lost on page reload.

Integrates with OpenAI's API by accepting a user-provided API key, sending board state and move requests to either gpt-3.5-turbo or gpt-4 endpoints, and parsing the LLM's text response to extract the move. The system handles API authentication, request formatting, and response parsing, but does not implement retry logic, rate limiting, or cost controls. Users are responsible for managing their own API keys and monitoring token usage.

Captures each move and its associated AI explanation in a chronological game log, displaying the log in a right-side pane that updates in real-time as moves are made. The log includes move notation (e.g., 'e2-e4') and the LLM's natural-language explanation of the move's strategic intent. The log is rendered as text in the UI and is not persisted beyond the current session.

Offers completely free access to the chess interface and gameplay without subscription fees or account creation. Users pay only for OpenAI API usage (typically $0.01-0.10 per game depending on move count and model selection). This model eliminates platform subscription costs but requires users to manage their own API credentials and monitor token usage. No freemium tier or trial credits are documented.